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Bayesian inference of stellar parameters and interstellar extinction using parallaxes and multiband photometry
Astrometric surveys provide the opportunity to measure the absolutemagnitudes of large numbers of stars, but only if the individualline-of-sight extinctions are known. Unfortunately, extinction is highlydegenerate with stellar effective temperature when estimated frombroad-band optical/infrared photometry. To address this problem, Iintroduce a Bayesian method for estimating the intrinsic parameters of astar and its line-of-sight extinction. It uses both photometry andparallaxes in a self-consistent manner in order to provide anon-parametric posterior probability distribution over the parameters.The method makes explicit use of domain knowledge by employing theHertzsprung-Russell Diagram (HRD) to constrain solutions and to ensurethat they respect stellar physics. I first demonstrate this method byusing it to estimate effective temperature and extinction from BVJHKdata for a set of artificially reddened Hipparcos stars, for whichaccurate effective temperatures have been estimated from high-resolutionspectroscopy. Using just the four colours, we see the expected strongdegeneracy (positive correlation) between the temperature andextinction. Introducing the parallax, apparent magnitude and the HRDreduces this degeneracy and improves both the precision (reduces theerror bars) and the accuracy of the parameter estimates, the latter byabout 35 per cent. The resulting accuracy is about 200 K in temperatureand 0.2 mag in extinction. I then apply the method to estimate theseparameters and absolute magnitudes for some 47 000 F, G, K Hipparcosstars which have been cross-matched with Two-Micron All-Sky Survey(2MASS). The method can easily be extended to incorporate the estimationof other parameters, in particular metallicity and surface gravity,making it particularly suitable for the analysis of the 109stars from Gaia.
| Near-infrared studies of the 2010 outburst of the recurrent nova U Scorpii
We present near-infrared (near-IR) observations of the 2010 outburst ofU Sco. JHK photometry is presented on 10 consecutive days starting from0.59d after outburst. Such photometry can gainfully be integrated into alarger data base of other multiwavelength data which aim tocomprehensively study the evolution of U Sco. Early near-IR spectra,starting from 0.56d after outburst, are presented and their generalcharacteristics discussed. Early in the eruption, we see very broadwings in several spectral lines, with tails extending up to~10000kms-1 along the line of sight; it is unexpected to havea nova with ejection velocities equal to those usually thought to beexclusive to supernovae. From recombination analysis, we estimate anupper limit of for the ejected mass.
| Walraven photometry of nearby southern OB associations
Homogeneous Walraven (VBLUW) photometry is presented for 5260 stars inthe regions of five nearby southern OB associations: Scorpio Centaurus(Sco OB2), Orion OB1, Canis Major OB1, Monoceros OB1, and Scutum OB2.Derived V and (B - V) in the Johnson system are included.
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Группы:
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Наблюдательные данные и астрометрия
| Созвездие: | Скорпион |
| Прямое восхождение: | 16h16m38.43s |
| Склонение: | -18°36'45.3" |
| Видимая звёздная величина: | 9.404 |
| Собственное движение RA: | -127.9 |
| Собственное движение Dec: | -37.2 |
| B-T magnitude: | 10.166 |
| V-T magnitude: | 9.467 |
Каталоги и обозначения:
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